Vowing never to part from his childhood friend Hisame, Itsuki journeys along the Tokaido with him in search of new adventures. As they exterminate youkai along the way, they rely on each other to complete the task. Though dark and mischievous, Itsuki appears to harbor a one-sided affection for Hisame; however, Hisame's naive nature prevents him from ever taking Itsuki seriously. Will Itsuki's efforts succeed, or will they prove futile?